Solve for $n$ : $2 = -9 + n$
Solution: Add $9$ to both sides: $ \begin{eqnarray} \\ \hphantom{2 {+ 9}} &\hphantom{=}& \hphantom{n} \\ 2 &=& -9 + n \\ \\ {+9} && {+9} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ 2 {+ 9} &=& n \\ \end{eqnarray} $ Simplify. $ n = 11$